Involuntary movements have often been difficult to classify clinically. Clinical and physiologic analysis of a continuing series of patients has led to new classifications and pathophysiologic insights. Patients with myoclonus have been studied to seek further understanding of this confusing involuntary movement. Detailed studies are in progress on the opsoclonus~myoclonus syndrome and on the phenomenon of negative myoclonus. Analysis is ongoing of the physiology of periodic movement in sleep. Extensive clinical and physiologic studies have continued in patients with palatal tremor (myoclonus). We have further data confirming the division of these patients into two groups, essential and symptomatic. A study of movement~related cortical potentials in patients with dystonia (hand cramps) has revealed an abnormality of cortical activation. This has been confirmed in additional studies with event~related desynchronization of the EEG. Motor performance in patients with dystonia (hand cramps) has shown a deficit in a task with rhythmic sequential movements. Patients tend to press the keys longer and their performance deteriorates with time. We have studied five patients with stiff~man syndrome in attempts to characterize the spinal and supraspinal mechanisms responsible for the generation of symptoms. Abnormalities of reflex mechanisms including lack of vibratory inhibition of H~reflex and abnormalities of reciprocal inhibition of the H~reflex were found in all patients indicating a dysfunction of normal inhibitory mechanisms involved in muscle relaxation.